[vesafb] Include raw status value within VBE error messages

Signed-off-by: Michael Brown <mcb30@ipxe.org>
[vesafb] Skip modes for which we cannot get mode information

The VirtualBox BIOS fails to retrieve mode information (with status
0x0100) for some modes within the mode list.  Skip any such modes,
rather than treating this as a fatal error.

Reported-by: Robin Smidsrød <robin@smidsrod.no>
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Merge branch 'master' into osimages